The taxonomy follows the view of the International Whaling Commission (IWC) Scientific Committee (IWC 2004) and the Convention on Migratory Species, which now recognize right whales in the North Atlantic, North Pacific and southern hemisphere as three distinct species in the genus Eubalaena, namely E. glacialis (North Atlantic Right Whale), E. japonica (North Pacific Right Whale) and E. australis (Southern Right Whale), based mainly on the mtDNA phylogenetic analyses of Rosenbaum et al. (2000).

In most of the scientific literature prior to 2000, including previous Red Lists (e.g. Baillie and Groombridge 1996), all northern hemisphere right whales are treated as the single species E. glacialis.

Rice (1998) classified right whales in the North Atlantic, North Pacific and southern hemisphere as the single species Balaena glacialis, in the genus Balaena along with B. mysticetus, the Bowhead Whale. While not all cetologists accept that the three right whale taxa qualify as full biological species, their clear geographical separation ensures that no practical problem arises from treating them as separate species.

Justification:
In view of how little is known about this species, and in the absence of evidence of a recovering trend, it is appropriate, pending analysis of more recent data, to base the assessment on the lower end of the range of the available abundance estimates, which are ~400 for the Okhotsk Sea and ~100 for the rest of the North Pacific, which implies a total of ~500, of which approximately half (~250) may be mature. It is therefore listed as Endangered under criterion D. Accumulation of new data over the next few years may lead to improved population estimates and a re-evaluation of the listing. A separate assessment has been developed for the eastern North Pacific subpopulation.

In the North Pacific, right whales occur during the summer in the Sea of Okhotsk, the southeastern Bering Sea, the Aleutian Islands, and the northern Gulf of Alaska. During the winter, they occur (or at least occurred historically) southward to the Sea of Japan [=East Sea], Taiwan Strait and the Ogasawara Gunto (Bonin Islands, Japan) in the west and to Baja California Sur (Mexico) in the east. Populations on the Asian and American sides of the Pacific are regarded as discrete (Brownell et al. 2001). Vagrants have been recorded in the Hawaiian islands (Rowntree et al. 1980, Herman et al. 1980).

Formerly abundant across much of the North Pacific in summer, mainly north of 40°N, the right whale is now regularly seen only in the Okhotsk Sea and the southeastern Bering Sea, with occasional sightings along the east coast of Japan, off the Bonin Islands, and in the Gulf of Alaska. In the 1970s there were two sightings off Hawaii (Salden and Mickelson 1999) in spring and three right whales were taken in the Yellow Sea in winter (Wang 1978, 1988). Sightings off California and Mexico are rare and there is no evidence that the western coasts of the United States and Mexico were ever highly frequented habitat for this species (Brownell et al. 2001).

The right whale population in the North Pacific is only a small fraction of what it was prior to 19th century whaling. A preliminary estimate of 26,500-37,000 animals taken (including struck and lost) during the period 1839-1909 was given by Scarff (2001), of which 21,000-30,000 were taken during 1840-49 alone.

Since the start of modern whaling in the North Pacific (1911), 742 right whales are recorded taken (Brownell et al. 2001) of which about 500 were illegal catches by Soviet whaling fleets in the 1960s, that were concealed at the time (Doroshenko 2000).

Brownell et al. (2001) listed a total of 1,965 right whale sighting records in the 20th century. Today, the main remnant population summers in the Sea of Okhotsk between Sakhalin Island and Kamchatka (Russian Federation). Based on sightings of 28 right whales in 2,688 nautical miles of Japanese-Russian cetacean surveys in the Okhotsk Sea in August and September in 1989, 1990 and 1992, Miyashita and Kato (1998) derived a preliminary population estimate of 922 whales (95% CI 404-2,108) using line-transect analysis. Additional Japanese surveys were conducted in 1999, 2000 and 2003 (Miyashita et al. 2000, 2001; Miyashita 2004). These yielded sightings of 23 right whales in 6,966 nautical miles of survey, but the data have not yet been analyzed to provide a population estimate. Given the low precision of the estimate from 1989-92, and the fact that the more recent surveys encountered relatively fewer right whales (3.3 whales per 1,000 miles in 1999-2003 compared with 10.4 whales per 1,000 miles in 1989-92), a new population estimate should be derived, using data from all the surveys to date. Sightings off Japan at other times of year may be whales migrating to or from the Okhotsk Sea.

In the eastern North Pacific, the few animals observed are usually alone and in scattered locations. The only exception is an area of the south-eastern Bering Sea where small groups of right whales have been seen in several successive years (LeDuc et al. 2001, Wade et al. 2006). No quantitative estimates of abundance outside the Okhotsk Sea are available, but the paucity of sightings suggests that right whales in the eastern North Pacific number only in the tens (Brownell et al. 2001). No confirmed sightings of calves were made in this region in the 20th century, and there have been only three thus far in the 21st (Waite et al. 2003, Wade et al. 2006).

Little is known about habitat use by North Pacific right whales. The rarity of coastal records in winter in either historical or recent times suggest that their breeding grounds may have been offshore (Clapham et al. 2004). This is in contrast to southern right whales which form inshore breeding concentrations. There is clearly some migration northward in summer and southward in winter (Clapham et al. 2004), but the location of the wintering grounds is unknown. The historical catches show that in summer the species mainly occurred in the Bering Sea, Gulf of Alaska, Sea of Okhotsk and northern North Pacific.

Hunting by the Japanese began as early as the late 1500s, and by Europeans and Americans in the 1830s; by 1900, the population had been reduced to a tiny fraction of its original abundance. Although legally protected by the IWC since 1946 (and by earlier agreements since 1935) illegal hunting continued into the 1960s, when Soviet whaling fleets killed 372 right whales in the eastern North Pacific, which may have been the bulk of the remaining population there (Doroshenko 2000, Brownell et al. 2001). The eastern North Pacific population is distinct and of extremely small size (fewer than 50 mature individuals); it is the subject of a separate assessment, as CR.

There is currently no direct hunting but there have been cases of known and suspected entanglements (Burdin et al. 2004) in the Okhotsk Sea and Kuril Islands, involving at least four whales including one dead. Effort is needed to ascertain the frequency of such occurrences, since the very low observer effort probably means that most deaths pass unrecorded.

As compared with the intensively studied North Atlantic right whale, the more offshore and remote distribution of the North Pacific right whale may be an advantage in terms of less intensive exposure to human impacts, but the disadvantage is that impacts that do occur are less likely to be detected and their consequences are harder to ascertain and evaluate.